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Hemi TECH

So I’ve been thinking about starting a Hemi TECH for all of you out there that want to build a hemi. Ive been planning a hemi build that is a bit different and not your typical build and definitely not a stocker.

This post is going to focus on early Hemi crank with a 3” stroke that I have had for several years. I originally bought this crank from and estate sale in Holley, MI with a bunch of left over parts from the A311-ex Indy program in 52’.

1951 - 1954 crankshafts for the 331 have a stock 3-5/8” stroke and 2-1/2” main bearing, 2-1/4” crankpin bearing journals.

For this build the crank I have has had to be modified to make the rotating assembly work in a stock 354 cuin block. The basic rotating asssembly consists of the 3” stroke crank, billet 7” length rods originally for a Chevy 454 tall deck and pistons that I speced out to Venolia to make it all work together. The final cubic inch displacement will be 301 cuin (4” bore x 3” stroke).

After doing the math for the relative piston speed I came up with 3750 fpm which is nothing for a forged slug! The pistons have a compression height of 1.889” = 7”rod x 1.5”stroke x 10.387” deck height and a 4”bore.

The crank pins are turned down to 2.200” for the BBC rods and I have polished the entire crank to mimic one of them high dollar Winberg or Bryant crank. Really easy to do. Tape up all your journals. I started with a 60grit type 27 zirconium flap disc and smoothed all the counter weights and crankpins out. Then I used mostly flat mill files to get the final finish contours and fought cut marks out. Probably the hardest part was sanding by hand everything with 120grit and moving to 220 grit, then green scotch bright and 0000 steel wool with metal polish/ green rouge on it.

All of this is so that the crank will shed oil rapidly and cut on the rotating mass windage drag.

I’m hoping so, I’m thinking 7000rpm is a realistic goal with the short block combination and the solid roller cam profiles I am working with. With a more modern roller profile from Howards Cams in Wisconsin in a naturally aspirated high compression trim this rotating assembly would be good to 8500 to 9000rpm with a good set of full groove main bearings.

Josh, I can tell you the next early hemi I build will be a standard rotating assembly...... no stroking or de-stroking, offset cranks, and mismatched parts.

Continuing with the Hemi tech, lets discuss timing options for the early 51 through 54 hemis with the long nose camshaft. (the long nose cams carried through on 354 cuin truck engines and industrial engine applications from 1957 until 1959)

Gary based out of Oregon is a really good source of early hemi information, his web site “quality engineered products” is mostly all Mopar. The URL for early hemi cam information is where you can easily see the differences of a early “long nose cam” and a more modern “short nose cam”.

Early long nose hemi cams are limited to the use of a stock timing set that works great for basic rebuilds but if you plan to turn any rpm or run any kind of roller cam with stiff springs you need to consider a double roller timing set. One of the ways you can do this is to track down a 57 through 59 timing set thats not worn beyond limits.

Or piece together a Melling S298 timing gear (replacement 57-59 upper gear) with 160 timing chain (Cloyes, Melling and several others make it: 0.865 wide, 68 links, 3/8 pitch, double roller chain) and a factory 273 HiPo or 1968 - 1970 340 lower crank gear (these were factory double roller timing sets that used the 3/8 pitch chain). Look at the 3rd & 5th pics, this is a set that I peiced together until I decided that I wanted more timing adjustability that are offered for via billet 9 way timing sets for small block Chrysler’s.

In pics 1 through 4, I modified an SA Gear pt no 78503-9 billet 9 way adjustable timing set. Originally I wanted to use just the bottom adjustable gear but the chain is not quite the same 3/8 pitch although it is really close. SA Gear is as far as I can tell American made in Chicago, at least the gears are anyways. To make this timing set work on the early long nose cams you will need to bore out the upper timing gear to fit the stock cam adapter and fuel pump eccentric.

Super easy to do, chuck up the upper gear on a lathe. I used a boring bar and turned out the ID to a final of 1.620” and faced the gear for a final thickness of 0.280”. All thats left is to locate and index the timing mark to the fuel pump eccentric and bore a 0.358” hole or T size drill. I just placed the S298 gear over the SA Gear , indexed the timing marks together and thats how I located the hole.

The main reason I went through all the trouble to use a long nose cam in lieu of a more readily available short nose cam is that I have three solid roller profiles that are from the early 50’s. They are in excellent shape and still usable. I did send them out to Ben Heirham at Howards Cams to have him read the cam lobe profiles and check them for straightness and polish up the lobe faces.

If you ever need cam work done, Howards is the place to do it! There absolutely top notch, very knowledgeable, and easy to work with!

The 1531555 cam is from one of the few factory prepped Windsor and Saratoga 331 race cars that ran in the 1953 Le PanAmerica Carrera Mexican Road Race. This is the proverbial “Pan Am” Cam that the old timers talked about.

The other two cams are from Chryslers A311-ex Indy engine program in 1952. These were in engines that were at first 331cuin and then 274cuin. Chrysler in 52 built half a dozen engines for the Kurtis Kraft K500 chassis that Firestone was using to test their new tires with. The cars were run at Chryslers test track oval and ran several miles an hour faster than the fastest Indy cars that year clocking over 185mph!.....AAA eventually got involved and that was that.

I cant figure out how to edit my previous post but the pics are a bit blurry, maybe these will be more readable.

All of the cams are below .500 lift but the intake center lines are really short! 106 through 109 dependent on the cam. You can definitely tell that these cams were designed with a slide rule and manually ground! When I look at the grinds to me they are way ahead of their time when you consider they were designed in 52’ and resemble modern lobe profiles. The intake and exhaust have fairly aggressive symmetrical lobe profiles as well even though the lift isn’t astronomical.

Lift on early hemis is limited to .500 anyways before the stock rocker arm height limits the arm geometry and the arm moves off the face of the valve tip..... that would be a bad day to drop a valve at rpm.

The 1531555 cam has a really nice lobe profile with a total lift of roughly .470ish between the intake /exhaust and 110 LSA and enough duration to keep it streetable and dual hat use with forced induction.